Eating but no drinking after shots

My cat got neutered and 2 shots in the same day. For the past 5 days, he has slept most of the day. His behind hurts. He eats regularly with appetite but he doesn't drink. I have forced it with syringe. I am worried. He still grooms himself after every meal, he loves being brushed. He stopped meowing g unless he is hungry. I am worried about the no drinking but he does pee once a day. Oh and I feed him raw chicken, the usual.

have you talked to the vet about this?

you could get canned food and stir in some water.  what does your cat do if you hold a water bowl near him and offer it without getting it right in his face?